There’s no easy answer to the question of how often prescribed burns or random wildfires should be used as a management tool. In fire-prone ecosystems, too little burning can be just as disastrous as too much burning. Many recommendations for fire regimes focus on maximizing diversity of fire type or maximizing heterogeneity of fire-age classes. However, these usually fail to take into account the demographic processes such as reproduction, growth, and dispersal of the species being burned.
New research that looks at a fire-prone ecosystem in Australia incorporates both demographic processes and landscape connectivity to find the best fire regime for maximizing biodiversity. Working in the South Coast Natural Resource Management region in the southwest corner of Western Australia (a biodiversity hotspot highly fragmented by agriculture), Tulloch et al. modeled the fate of seven species in a keystone genus (Banksia sp.) over 100 years under various fire regimes and landscape contexts. Their goal was to determine how to maximize Banksia diversity in a given patch through fire management, knowing that current fire management plans often change based on the degree of landscape connectivity.
Their results give no black and white number on how often to burn, but they do provide guidance for managers looking to sort through the numerous considerations that are part of a fire regime. No single fire regime applied uniformly across the landscape was able to maintain all seven species in every patch containing them. A more effective strategy would be to apply different fire regimes to different patches, so that all species were retained somewhere in the landscape, but not necessarily in all patches. Patch connectivity changed the tolerance of species to fire intervals, mostly because Banksia sp. are poor dispersers. In unconnected landscapes, only using prescribed fires, or a mix of prescribed fires and wildfires, appears to be a viable management strategy. However, in connected landscapes, managing with both prescribed fires and wildfires would have catastrophic consequences for Banksia.
There is no ideal fire regime, especially in a highly fragmented landscape. Prescribed fire can be helpful or harmful, depending on how connected a patch is in the landscape. By combining information on both the demography of target species and landscape connectivity, managers of fire-prone ecosystems can hope to maintain high levels of biodiversity over the long term.
Tulloch, A.I.T., J. B. Pichancourt, C. R. Gosper, A. Sanders, and I. Chadès. 2016. Fire management strategies to maintain species population processes in a fragmented landscape of fire‐interval extremes. Ecological Applications 26(7): 2175-2189.